The 260 °C phase equilibria of the Sn–Sb–Ag ternary system and interfacial reactions at the Sn–Sb/Ag joints

The isothermal section of the Sn–Sb–Ag ternary system at 260 °C has been determined in this study by experimental examination. Experimental results show no existence of ternary compounds in the Sn–Sb–Ag system. Two extensive regions of mutual solubility have been determined. The one located between the two binary isomorphous phases, Ag₃Sn and Ag₃Sb, is labeled as and the other one located between the two binary isomorphous phases, Ag₄Sn and Ag₄Sb, is labeled as ξ. The phase is a very stable phase and is in equilibrium with ξ, Sb, SbSn, Sb₂Sn₃, and liquid Sn phases. Each of the Sb and SbSn phases has a limited solubility of Ag. Only one stoichiometric compound, Sb₂Sn₃, exists. Besides phase equilibria determination, the interfacial reactions between the Sn–Sb alloys and the Ag substrate were investigated at 260 °C. It was found that the phase formations in the Sn–Sb/Ag couples are very similar to those in the Sn/Ag couples.     

An investigation of the Pd–Ag–Ru–Gd quaternary system phase diagram

On the basis of the Ag–Pd–Gd, Ag–Ru–Gd and Pd–Ru–Gd ternary systems, the partial phase diagram of Pd–Ag–Ru–Gd (Gd < 25 at.%) quaternary system has been studied by means of X-ray diffraction analysis, differential thermal analysis, electron probe microanalysis and optical microscopy. The 700 °C isothermal sections of the Ag–Pd–5Ru–Gd, Ag–Pd–20Ru–Gd and Ag–Pd–50Ru–Gd (Gd ≤ 25 at.%) phase diagrams were determined, respectively. And the 700 °C isothermal section of the Pd–Ag–Ru–Gd (Gd ≤ 25 at.%) quaternary system phase diagram was finally inferred. The section consists of four single-phase regions: solid solution Pd(Ag), (Ru), Pd₃Gd and Ag₅₁Gd₁₄; five two-phase regions: Pd(Ag) + (Ru), Pd(Ag) + Ag₅₁Gd₁₄, (Ru) + Ag₅₁Gd₁₄, Pd(Ag) + Pd₃Gd and (Ru) + Pd₃Gd; three three-phase regions: Pd(Ag) + Pd₃Gd + (Ru), Pd(Ag) + Ag₅₁Gd₁₄ + (Ru) and (Ru) + Ag₅₁Gd₁₄ + Pd₃Gd; one four-phase region Pd(Ag) + (Ru) + Ag₅₁Gd₁₄ + Pd₃Gd. No new quaternary intermetallic phase has been found.     

Hydrogen absorption properties of Li–Mg–N–H system

Isothermal hydrogen absorption properties of the ball milled mixture of 3Mg(NH₂)₂ and 8LiH after dehydrogenation at 200 °C under high vacuum were investigated at two different temperatures of 150 and 200 °C. The pressure–composition isotherm (PCT) curve at 200 °C revealed a two-plateaus-like behavior, while the PCT curve at 150 °C showed a single-plateau-like behavior. The hydrogenated phases were composed of LiH and Mg(NH₂)₂ under 9 MPa at 200 °C, while those were observed as mixed phases of LiH and LiNH₂ at 150 °C without any trace of Mg(NH₂)₂ in XRD measurements. These results indicate that there are two-step hydrogenation processes corresponding to high and low pressures at 200 °C, but the kinetics at 150 °C is too slow to proceed with the second hydrogenating step at high pressure region.     

Influence of WC addition on the microstructure and mechanical properties of NbC–Co cermets

NbC–24.5 wt.% Co cermets with up to 30 wt.% WC were obtained by solid state hot pressing at 1300 °C under a pressure of 45 MPa for 10 min and pressureless liquid phase sintering at 1360 °C for 60 min. The effect of WC addition on the microstructure and mechanical properties of NbC–Co based cermets was investigated. The hot pressed cermets exhibited interconnected and irregular niobium carbide (NbC) or (Nb,W)C grains, whereas the shape of the NbC grains changed from faceted with rounded corners to spherical, as the WC content increased in the pressureless sintered cermets. The undissolved WC increased with increasing WC addition. A clear core/rim structure was observed in the hot pressed cermets with 10–30 wt.% WC additions, whereas this structure was gradually eliminated when pressureless sintering. The hardness remains nearly constant whereas the fracture toughness slightly increases with increasing WC addition. The dissolution of WC in the Co binder and NbC grains, as well as the formation of a solid solution (Nb,W)C phase were supported by thermodynamic calculations.     

Investigation on the phase relationships in the Ir–Nb–Ni–Al system at the Ni-rich side

The phase relationship of the quaternary system Ir–Nb–Ni–Al for the Ni-corner was experimentally studied by investigating two newly produced alloys and testing the phase compositions of seven alloys previously investigated. The partial phase relationship around the Ni-rich side at 1300 °C was established.     

Phase equilibria and thermal analysis of Si–C–N ceramics

The phase reactions, crystallization behaviour and thermal degradation of two Si–C–N ceramics derived from precursors VT50 and NCP200, respectively, were studied by means of CALPHAD type thermodynamic calculations and experimental investigations by DTA/TG, XRD and SEM/EDX. The phase reaction Si₃N₄+3C=3SiC+2N₂ proceeds during the thermal degradation of both ceramics. Additionally, the phase reaction Si₃N₄=3Si+2N₂ occurs during the thermal degradation of the NCP200 ceramic. To explain quantitatively the high temperature behaviour of Si–C–N ceramics, thermodynamic functions, the reaction scheme, isothermal sections, isopleths, phase fraction diagrams and phase composition diagrams (for gas partial pressures) were calculated. The computer simulations were confirmed by the experiments for both ceramics.     

Phase equilibria in the Fe–Al–Mo system – Part I: Stability of the Laves phase Fe2Mo and isothermal section at 800 °C

Phase equilibria in the Fe–Al–Mo system were experimentally determined at 800 °C. From metallography, X-ray diffraction and electron probe microanalysis on equilibrated alloys and diffusion couples a complete isothermal section has been established. It is shown that the Laves phase Fe₂Mo is a stable phase. The phase Al₄Mo, which only becomes stable above 942 °C in the binary system, is the only ternary compound found at 800 °C. For all binary phases the solid solubility ranges for the third component have been established. The D0₃/B2 and B2/A2 transition temperatures have been determined for a selected alloy by differential thermal analysis and transmission electron microscopy. The results confirm that the D0₃/B2 transition temperature substantially increases by the addition of Mo, while the B2/A2 transition temperature is about that for a binary alloy with the same Al content.     

Evaluation of hydrogen absorption properties of Ti–0.2 mass% Pd alloy in fluoride solutions

The hydrogen absorption properties of Ti–0.2 mass% Pd (Ti–0.2Pd) alloy in 2.0% and 0.2% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solutions (25 °C) has been evaluated by hydrogen thermal desorption analysis. During the early stage of immersion (120 h) in the 2.0% APF solution, the amount of absorbed hydrogen was lower than 500 mass ppm. A thermal desorption of hydrogen primary appearing with a peak at 500–600 °C and a broad desorption ranging from 100 to 400 °C were observed. In the 0.2% APF solution, the amount of absorbed hydrogen saturated at 100–200 mass ppm; the thermal desorption of hydrogen appeared with a single peak at 550 °C. In the 2.0% NaF solution, hydrogen absorption was negligible even after 1000 h of immersion, although corrosion pits were observed. The results of the present study suggest that the hydrogen absorption of Ti–0.2Pd alloy, as compared with commercial pure titanium, is suppressed in fluoride solutions.     

Turning of glass–fiber reinforced plastics materials with chamfered main cutting edge carbide tools

In this paper, the machinability of high-strength glass–fiber reinforced plastics (GFRP) materials in turning with chamfered main cutting edge of P and K type carbide tools have been investigated experimentally. Chip formation mechanisms have been obtained with respect to tip's geometries and nose radii. Experimental results for cutting forces were also taken with GFRP as the workpiece material. Force data from these tests were used to estimate the empirical constants of the mechanical model and verify its prediction capabilities. The results show good agreement between the predicted and measured forces. In this study, the nose radius R = 0.3 mm induces a decrease of the cutting force and the smallest cutting force values was achieved in the case of C_s = 20°, _S1(_S2) = −10°(10°) and R = 0.3 mm. Comparing the different P and K type of tools, K type tool is better than P type of chamfered main cutting edge tools. The theoretical values of cutting forces were calculated and compared with the experimental results; the forces predicted by this model were consistent with the experimental values.     

Ti–V–Mn based alloys for hydrogen compression system

Ti–V–Mn based hydrides are one family of alloys with improved hydrogenation properties and they have a great potential to replace the AB₅ alloys as the sorption materials in hydrogen compression systems, although there still are many problems associated with their use, including unstable reversible hydrogen capacity and unfavorable thermodynamic properties. To gain a better understanding on the effect of the substitution elements and to optimize the alloy composition for high storage capacity, the influence of the alloy stoichiometry was investigated. Ti–Zr–V–Mn alloys were prepared by arc melting technique and were annealed in vacuum at temperature above 900 °C to obtain great sorption properties. Hydrogen absorption and desorption kinetics and PCT characteristics of these alloys at ambient temperature were measured and compared. These hydrogen storage features were also discussed in relation to the effect of alloy element compositions. Ti–Zr–V–Mn alloy cycling behavior was also examined.     

Thermodynamic optimisation of the Pb–Tl binary system

The phase diagram of the Pb–Tl binary system is experimentally well determined. Experimental thermodynamic values for all the phases involved are also available. For the liquid phase the temperature dependence of the enthalpy of mixing is also determined. In the present contribution, a consistent set of Gibbs energy functions of all the phases is obtained using the Redlich–Kister polynomial. The adjustable model parameters were determined by least-squares fit to the experimental data. A satisfactory agreement between experimental and calculated values is observed.     

Observation of hydrogen absorption/desorption reaction processes in Li–Mg–N–H system by in-situ X-ray diffractmetry

The in-situ XRD measurements on dehydrogenation/rehydrogenation of the Li–Mg–N–H system were performed in this work. The ballmilled mixture of 8LiH and 3Mg(NH₂)₂ as a hydrogenated phase gradually changed into Li₂NH as a dehydrogenated phase during heat-treatment at 200 °C in vacuum for 50 h. Neither Mg-related phases nor other intermediate phases were recognized in the dehydrogenated phase. With respect to the hydrogenation process, the dehydrogenated state gradually returned to the mixed phase of the LiH and Mg(NH₂)₂ without appearance of any intermediate phases during heat treatment at 200 °C under 5 MPa H₂ for 37 h and during slow cooling down to room temperature through 24 h. In the hydrogenation process at 200 °C under 1 MPa H₂, however, the growing up of the LiNH₂ and LiH phase was observed in the XRD profiles before the 3Mg(NH₂)₂ and 8LiH phases were formed as the final hydrogenated state. This indicates that the LiNH₂ and LiH phase essentially appears as an intermediate state in the Li–Mg–N–H system composed of 3Mg(NH₂)₂ and 8LiH.     

Synthesis mechanisms of lithium cobalt oxide prepared by hydrothermal–electrochemical method

Thermodynamic calculation method was adopted to predict the reaction mechanism of LiCoO₂ prepared by hydrothermal–electrochemical process. It was found that in the Co–LiOH–H₂O system, Co was oxidized to HCoO₂⁻, Co(OH)₂ (100 °C) or CoO (150 °C), CoOOH in sequence with the increase of electrode potential, then the ion-exchange reaction of CoOOH and lithium ion occurred and LiCoO₂ came into being. The optimum synthesis parameter was obtained through thermodynamic calculation and it was validated experimentally by cyclic voltammogram method.     

The ternary system Na2O–ZnO–WO3: Compounds and phase relationships

The subsolidus phase relationships of ternary system Na₂O–ZnO–WO₃ have been investigated by X-ray diffraction (XRD) and differential thermal analyzer (DTA). All the samples were synthesized in the temperature range from 530 to 850 °C in air. There are one ternary compound and five binary compounds in the Na₂O–ZnO–WO₃ system, which can be divided into eight three-phase regions. The crystal structure of the ternary compound Na_3.6Zn_1.2(WO₄)₃ is determined by single-crystal structure analysis method. It belongs to triclinic system with space group and lattice constants a = 7.237 (5) Å, b = 9.172 (6) Å, c = 9.339 (6) Å and  = 94.920 (4)°, β = 105.772 (9)°, γ = 103.531 (8)°, Z = 2. DTA analyses indicate that the compound Na₂WO₄ is not suitable to be the flux for ZnO crystal growth below 1250 °C, since no liquidus was observed in the system before 1250 °C.